Agriculture Reference
In-Depth Information
requirements of uniformity and stability are there to
protect the growers and to ensure that they are being sold
something that will grow and exhibit the characteristics
described by the breeder.
The further requirement of any new cultivar, is
perhaps obvious, but nevertheless is a statutory require-
ment in many countries and referred to as
value
for
cultivation
and
use
(VCU). VCU can be determined
by two primary methods and there will always be debate
regarding which system is better. In the United King-
dom, which organizes statutory trials, VCU is described
as follows: '
The quality of the plant variety shall in com-
parison with the qualities of other plant varieties in a
national list, constitute either generally or as far as produc-
tion in a specific area is concerned, a clear improvement
either as regards crop farming or the use made of harvested
crops or of products produced from these crops. The Qual-
ities of the plant variety shall for this purpose be taken as
a whole, and inferiority in respect of certain characteristics
may be offset by other favourable characteristics
'.
In a few countries (including the United States) any
plant breeder can sell seed from a cultivar developed
and registered, irrespective of how well adapted it is to
a given region or how productive the cultivar is likely to
be. The choice of which cultivar to grow is left entirely
to farmers and producers. It is common that farmers will
allot a small proportion of the farm to plant a new culti-
var, and if acceptable, will increase hectarage with time.
Obviously, unadapted cultivars or those, which have
inferior end-use quality, are unlikely to gain in acreage
in this way. Similarly, companies (seed or breeding) and
organizations rely on their reputation to sell their prod-
ucts and reputations can easily be tarnished by releasing
and selling inferior products.
However, it is more common that countries have
statutorily organized trialling schemes to determine
VCU of cultivars that are to be released. This testing
is usually conducted over two or three years, in a range
of environments that the cultivars are likely to be grown.
If breeding lines perform better than cultivars already
available in that country, then government authorities
will place that cultivar on the National List. Only culti-
vars that are included on the National List are eligible for
propagation in that country. In some countries, newly
listed cultivars also are entered into further statutory
trials for one to two additional years. Based on per-
formance in these extra years' trials, cultivars may be
added to a
Recommended Varieties List
. This effectively
means that the government authority or testing agency
is recommending that is would be a suitable new cul-
tivar for farmers to consider. The theoretical advantage
of statutory VCU testing is that it only allows 'the very
best cultivars' to be grown and prevents unadapted cul-
tivars from being sold to farmers. The major drawbacks
of the
Regulatory Trialling
schemes are:
Mistakes are inevitably made (although it is difficult
to estimate at what rate) in that potentially desirable
adapted new cultivars simply do not do well in the
test conditions, for whatever reason. In this situation
the cultivar is removed from further screening and all
the time and effort expended by the breeder on that
genotype's development would have been wasted.
•
Authorities (or their agents), who organize these tri-
als are often limited by resources and cannot always
evaluate the number of test entries that may be sub-
mitted as thoroughly as might be desirable. In these
situations there is often a 'lottery system' introduced
where: companies are allowed to enter
a certain num-
ber
of test entries; not all entries are grown in all trial
sites; and a non-comprehensive set of control cultivars
included.
•
Statutory trials suffer the same deficiencies as all small
plot evaluation tests: they do not always reproduce or
mimic the conditions or situations that occur on a
realistic scale of production.
•
They delay the period from a cultivar being developed
to when it is released for commercial production. In
some crop species (e.g. potato) this is not a great prob-
lem as the rate of increase of seed tubers in potato
is low and it would normally take several years to
increase sufficient tuber seeds to be planted on a
commercial scale (a rate of increase of approximately
10:1). However, in other seed crops, for example
rapeseed (oilseed rape), the rate of seed increase (par-
ticularly if off-season increase is possible) can be
considerable, around 1000:1, and a three to four year
delay in release can be costly to breeding companies.
•
The criteria for judging both DUS and VCU will
be strongly determined by the type of species, partic-
ularly its mode of reproduction and multiplication for
production.
MODES OF REPRODUCTION
It is essential to have an understanding of the mode(s)
of reproduction prior to the onset of a plant breeding
